Polyphenylene sulfide resin composition is widely used for electrical and electronic components and automobile parts because it is provided with well-balanced properties such as excellent mechanical properties, heat resistance, chemical resistance and thin fluidity.
Conventionally, in case of resin molded product of complicated shape, a plurality of separated parts are molded beforehand, then these parts are integrally bonded to obtain a product of complicated shape. As means for integrally bonding a plurality of parts in such a manner, bonding by adhesive agent, mechanical bonding with bolt or the like, bonding by external heat welding such as laser welding, hot plate welding, and bonding by friction heat welding such as vibration welding, ultrasonic welding have been used. Among these means, it is difficult to obtain high bonding strength by the bonding with bonding agent, and the mechanical bonding requires more cost and labor and, moreover, causes weight increase. However, bonding by external heat welding or friction heat welding has been increasingly used in recent years, because it doesn't use extra material such as adhesive agents or bolts and, moreover, it doesn't causes problems such as an environmental pollution, weight increase.
Among the aforementioned external heat welding, the laser welding method, in particular, has an advantage of being performed easily. The laser welding method for two resin molded products, as disclosed for instance in JP S60-214931 A1, is executed by irradiating laser beam from one of superposed two molded products to the other. The laser beam transmits through the molded product of irradiating side to be absorbed into the molded product of the other side and melts the resin to fuse and bond both molded products therebetween. Therefore, it is essential for laser welding method that the laser beam transmits through the molded product of irradiation side into the other molded product. Consequently, two molded products can not be bonded, or a sufficient bonding strength can not be obtained, if a resin material with low laser beam transmittance is used for the molded product into which the laser beam transmits.
Whereas, the aforementioned polyphenylene sulfide resin of high crystallinity is characterized by significantly low laser beam transmittance. Therefore, in case of using polyphenylene sulfide resin composition for a molded product of laser beam transmitting side in the laser welding method, it has been necessary to thin the molded product so as to transmit the laser beam. Consequently, in case of bonding polyphenylene sulfide resin composition by the laser welding method, there has been a problem that degree of freedom for design of the molded product becomes inevitably low.
It could therefore be helpful to provide a polyphenylene sulfide resin composition capable of obtaining excellent laser weldability and heat resistance without lowering the degree of freedom for design of the molded product, even when used for the molded product of laser beam transmitting side in the laser welding method.
It could also be helpful to provide a polyphenylene sulfide resin composition with excellent low warpage properties that reduces the generation of warpage when it is molded.